What is Neck Up?
1.
The act of forcing ones premature departure from a non relevant discussion, whilst holding your thumb perpendicular to your neck and index finger directly toward the sky.
In the words of Chopper "Neck up, parrot"
2.
Neck up means to ask someone to stop speaking un-truths. And it also is a non polite way to persuade a person or individuals to cease their conversation, or to "shut up".
Hodgo: "Union players are all gay champ, bogans are fairdinkum tops"
Jango Fett: "Neck up cocksmoke/belter!"
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3.
To tell a person to commit suicide by means of hanging.
"Why don't you do yourself a favour and neck up you cunt? Your a Parrot! Fucking blowfly.." Keithy Goerge to Chopper
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4.
the process of downing a beer
Dave: your shit.
John: neck up you clown!
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5.
inserting head up anus till neck is up the anal cavity
neck up you fuckhead